In recent years, a low-profile connector is practically used for connecting electric circuits formed on two circuit boards (including flexible printed circuit board) in a manner so that the circuit boards face each other. In mobile equipment such as a mobile phone, the connector is required to be downsized and to have a low profile corresponding to the miniaturization and the low profile of the mobile equipment. On the other hand, a packaging density of the electronic components mounted on the circuit board becomes higher due to high functionality of the mobile equipment, so that number of arrangement of contacts constituting the connector is tend to be increased and the width and pitch of arrangement of the contacts become much narrower. Especially in a flip phone, the circuit boards, on which the electronic components are mounted, are separately disposed on both sides with respect to a hinge, and flexible substrates provided in the inside of the hinge are used for connecting the separated circuit boards. Thus, the application of the connector will be expanded for connecting the circuit boards each other or connecting the electronic components and the circuit boards.
The connector for connecting two circuit boards is constituted by a header corresponding to a male connector mounted on one circuit board and a socket corresponding to a female connector mounted on the other circuit board.
FIG. 29 shows sectional views of a socket 201 and a header 210 of a conventional connector. The socket 201 comprises a socket body 202 and a plurality of pairs of contacts 204. The socket body 202 is made of resin molding and has a pair of elongate recesses 203 formed along both sidewalls 202a of the socket body 202 and a center table portion 215. A plurality of fitting grooves 202b are formed at a predetermined pitch on both sidewalls 202a of the socket body 202 in a direction perpendicular to the paper sheet of FIG. 29. Each contact 204 is made of a conductive metal thin plate so as to have a U-shaped plate spring portion 205, a reverse U-shaped fitting portion 206 and a soldering terminal 207, which are integrally formed. Each fitting portion 206 of the contact 204 is press-fitted into the fitting groove 202b on the sidewall 202a so as to grip the sidewall 202a. The soldering terminal 207, which is to be soldered on a circuit board, is formed by bending a rear end portion of the contact 204 toward the outside from a rear end of the fitting portion 206. The plate spring portion 205 is formed to have a U-shape by bending a front end portion of the contact 204 from a front end of the fitting portion 206, so that the plate spring portion 205 is disposed in the recess 203 so as to be warped freely. A front end of the plate spring portion 205 is doglegged so as to form a contacting portion 209.
The header 210 comprises a header body 211 and a plurality of pairs of posts 212. The header body 211 is made of resin molding and has a groove 211a which engages with the table portion 215 of the socket body 202 of the socket 201. The post 212 is made of a conductive metal thin plate by bending substantially reverse L-shape. A rear portion of the post 212 protruding toward the outside serves as a soldering terminal 214 which is to be soldered on a circuit board. Each post 212 is fixed on the header body 211, since a base of the post 212 is inserted into the header body 211 while the header body 211 is molded in a manner so that the pairs of posts 212 are arranged at the predetermined pitch in the direction perpendicular to the paper sheet of FIG. 29.
FIG. 30 shows a state that the socket 201 and the header 210 are coupled with each other. For coupling the socket 201 with the header 210, the table portion 215 of the socket body 202 of the socket 201 is fitted into the groove 211a of the header body 211 of the header 210. At that time, a curved lower end 212a of the post 212 of the header 210 contacts a slanted face at an upper end of the plate spring portion 205 of the contact 204, so that the plate spring portion 204a of the contact 204 is warped inwardly. Subsequently, the post 212 and a sidewall of the header body 211 of the header 210 are disposed between a side face of the table portion 215 and the contact 204 of the socket 201. Thus, the contacting portion 209 of the contact 204 elastically contacts with a side face of the post 212.
In such the connector, it is required to making the mounting areas of the socket and the header much narrower corresponding to the downsizing of the mobile equipment. Furthermore, it is required to provide a low-profile connector corresponding to the low profile of the mobile equipment using the circuit boards. Actually, a connecter having a pitch 0.3 to 0.5 mm of arrangement of the contacts of the socket and the posts of the header is supplied. Furthermore, a low-profile connector having a thickness called stacking height less than 1.5 mm (for example, 1.2 mm or 1.0 mm) when the header is coupled with the socket is also provided.
It is further required to make the pitch of the contacts much narrower and to make the stacking height of the connector much lower. Concretely, it is required to make the stacking height of the connector less than 1.0 mm. When the stacking height between a lower face of the soldering terminal 207 of the contact 204 of the socket 201 and an upper face the soldering terminal 214 of the post 212 of the header 210 in the above-mentioned conventional connector is made much thinner in a range between 0.9 mm to 0.8 mm, there is a limit to lengthen the length of the plate spring portion 205 of the contact 204, so that the spring characteristics of the plate spring portion 205 of the contact 204 cannot be increased. Thus, a sufficient contact pressure cannot be obtained between the plate spring portion 205 of the contact 204 and the post 212. Furthermore, when a dimension “C” between a peak of the contact portion 209 and a base of a side 206a of the fitting portion 206 of the contact 204 is made larger than a dimension “D” between the base of the side 206a and a base of the plate spring portion 205, the stress concentration occurs at the bent corner of the U-shaped plate spring portion 205 when the plate spring portion 205 is warped. Still furthermore, the shear plane at top end of the contact 204 is caught on the header 210 when the header 210 is coupled with the socket 201, so that the contact 204 may be deformed.
Still furthermore, when the stacking height of the connector is made thinner, it is necessary to make the socket body 202 of the socket 201 and the header body 211 of the header 210 thinner. Thus, there is a possibility that the thickness of the sidewalls and bottom wall of the bodies 202 and 211 become too thin to maintain a practical strength. In other words, contortion and/or crack can easily occur in the socket body 202 of the socket 201 and the header body 211 of the header 210 due to the stress generated in the socket 201 and the header 210 while the socket 201 and the header 210 are treated or mounted on the circuit boards.